At least in public, Republicans have been clear that they see the current budget negotiations as a chance to address what they see as the source of Washington's deficit problem: major entitlement programs.

"Medicare and Social Security and Medicaid, if those aren't fixed, if we're not honest about how to fix them, and the fact that, yes, everybody in this country will have to participate in some discomfort if we're going to get out of this hole," said Sen. Tom Coburn, R-Okla., on ABC's This Week last Sunday.

But if Republicans have drawn a line in the sand insisting that those major programs be put on the table for negotiation, Democrats are drawing a line of their own. They say Medicaid, which serves the health care needs of some 60 million low-income Americans, needs to be taken off the table.

"Any cut in Medicaid will be felt by our most vulnerable," Sen. Ben Cardin, D-Md., said Tuesday at a news conference on Capitol Hill. "We can't let that happen. That's what's at stake."

Cardin was joined by nearly a dozen other House and Senate Democrats who urged Democratic negotiators to leave the program alone.

Maryland Rep. Chris Van Hollen, the ranking member on the House Budget Committee, said Medicaid is already stretched too thin.

"It's stretched so thin that if you stretch it any more you will rip a big hole in that safety net and millions of Americans will fall through and get badly hurt," he said.

But Democrats have another reason to worry about the possibility of cuts to Medicaid; one that goes beyond the impact on the people it serves. It has to do with the federal health law, the Affordable Care Act. The law calls for expanding Medicaid to as many as 16 million more people, and the federal government has promised states it will pay most of those additional costs.

"If they target Medicaid as part of entitlement reform," he says, that could be a deciding factor for many.

Ron Pollack, of the consumer group Families USA, is even more emphatic about keeping Medicaid protected from cuts to preserve the health law's future.

"If this budget negotiation results in reducing the Medicaid program, then I think that governors are not going to opt into this expansion," he said. "So it is now essential to protect the Medicaid program."

That sentiment is hardly universal, however.

Merrill Matthews, a resident scholar with the conservative Institute for Policy Innovation, is one of many conservatives who think Medicaid needs a complete overhaul.

"Although it's better than not having any insurance, it is bad insurance," he says of Medicaid. "And I argue that health care coverage for the poor shouldn't necessarily be poor coverage."

All of which sets up just one more major area of disagreement as the clock ticks down on the budget negotiators.

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DAVID GREENE, HOST:

Here in Washington, the debate is over the federal budget. Republicans insist they will not agree to raise taxes on the wealthy unless Democrats agree to cut spending on the two huge national health programs, Medicare and Medicaid. Democrats say they're willing to talk about reducing Medicare, but as NPR's Julie Rover reports, Medicaid is another story.

JULIE ROVNER, BYLINE: In all the public discussions to avert the so-called fiscal cliff, Republicans have made one thing clear. They want to address what they see as the source of Washington's deficit problem: major entitlement programs. Here's how Oklahoma Senator Tom Coburn put it Sunday on ABC's "This Week."

(SOUNDBITE OF TV SHOW "THIS WEEK")

SENATOR TOM COBURN: Medicare and Social Security and Medicaid, if those aren't fixed, if we're not honest about how to fix them, and the fact that, yes, everybody in this country will have to participate in some discomfort if we're going to get out of this hole.

ROVNER: But if Republicans have drawn a line in the sand insisting that those major programs be put on the table for negotiation, Democrats are drawing a line of their own. They say Medicaid, which serves the health care needs of some 60 million low-income Americans, needs to be taken off the table now.

SENATOR BEN CARDIN: Any cut in Medicaid will be felt by our most vulnerable. We can't let that happen. That's what's at stake.

ROVNER: Ben Cardin is a Democratic senator from Maryland. He was joined at a news conference yesterday on Capitol Hill by nearly a dozen other House and Senate Democrats who urged Democratic negotiators to leave the program alone. Maryland congressman and Budget Committee ranking member Chris Van Hollen said Medicaid is already stretched too thin.

REPRESENTATIVE CHRIS VAN HOLLEN: It's stretched so thin that if you stretch it any more you will rip a big hole in that safety net and millions of Americans will fall through and get badly hurt.

ROVNER: But there's another reason Democrats are worried about the possibility of cuts to Medicaid that goes beyond the impact on the people it serves. It has to do with the federal health law, the Affordable Care Act. The law calls for expanding Medicaid to as many as 16 million more people, and the federal government has promised states it will pay most of those additional costs.

MATT SALO: One of the questions states have had, and still have, is will Congress keep its promises?

ROVNER: Matt Salo is executive director of the National Association of Medicaid Directors. He's one of many who think that governors deciding whether or not to go ahead with the expansion are watching these budget talks very closely.

SALO: And if they target Medicaid as part of entitlement reform, that could make a big decision in states saying yes or no.

ROVNER: Ron Pollack, of the consumer group Families USA, is even more emphatic about keeping Medicaid protected from cuts to preserve the health law's future.

RON POLLACK: So if this budget negotiation results in reducing the Medicaid program, then I think governors are not going to opt into this expansion so it is now essential to protect the Medicaid program.

ROVNER: But that's not a universal sentiment. Merrill Matthews is a resident scholar with the conservative Institute for Policy Innovation. Like many conservatives, he thinks Medicaid needs a complete overhaul.

MERRILL MATTHEWS: Although it's better than not having any insurance, it is bad insurance. And I argue that health coverage for the poor shouldn't necessarily be poor coverage.

ROVNER: Which sets up just one more major area of disagreement as the clock ticks down on the budget negotiators. Julie Rovner, NPR News, Washington. Transcript provided by NPR, Copyright NPR.